Beasts are a category of enemy in Final Fantasy XI, and a significant part of the game's ecosystem. Beasts predate lizards, and gain a bonus to their damage against them in addition to inflicting their natural Killer ability. Conversely, Plantoids gain a bonus to damage against beasts, and their Killer ability means that Beasts will periodically freeze up when attacking them. There are several distinct families of creature within the Beast classification, including Behemoths, Buffalo, Cerberi, Coeurls, Dhalmel, Gnoles, Manticores, Marid, Opo-opo, Rabbits, Rams, Sheep, and Tigers.

Known as Beastkin, this refers to all quadrupedal mammalian creatures in Eorzea such as coeurls and sheep, and is one of the most diverse groups in Eorzea. Many tend to drop skins and pelts used for Leatherworking.